Resistance

Drug resistance

Growing resistance to antimalarial medicines has spread very rapidly, undermining malaria control efforts.

When treated with an artemisinin-based monotherapy, patients may discontinue treatment early following the rapid clearance of malaria symptoms. This results in partial treatment and patients still have persistent parasites in their blood. Without a second drug given as part of a combination (as is done with an ACT), these resistant parasites survive and can be passed on to a mosquito and then another person. Monotherapies are therefore the primary force behind the spread of artemisinin resistance.

If resistance to artemisinins develops and spreads to other large geographical areas, as has happened before with chloroquine and sulfacoxine-pyrimethamine (SP), the public health consequences could be dire, as no alternative antimalarial medicines will be available in the near future.

WHO recommends the routine monitoring of antimalarial drug resistance, and supports countries to strengthen their efforts in this important area of work.

Insecticide resistance

Mosquito control is being strengthened in many areas, but there are significant challenges, including:

  • an increasing mosquito resistance to insecticides, including DDT and pyrethroids, particularly in Africa; and
  • a lack of alternative, cost-effective and safe insecticides.

The development of new, alternative insecticides is an expensive and long-term endeavour. Detection of insecticide resistance should be an essential component of all national malaria control efforts to ensure that the most effective vector control methods are being used. The choice of insecticide for IRS is a decision that should always be informed by local and recent data on the susceptibility of the target vectors, and ensuring the availability of such data is a shared responsibility.